This is now solved. We did not want to publish the printers before they would be fully configured, so our Windows administrators removed read rights from samba server object's security descriptor "Authenticated Users".
Analyzing the network traffic released, that DC didn't return any LDAP attributes to the samba servers LDAP search request. "Surprisingly" giving read rights to the Authenticated Users security descriptor solved this problem.
However, I still think this as a bug, because it shouldn't cause smbd to panic during restart. If requested, I can provide thorough information for developers to fix this.
BR,
Antti